Automatic coffee brewers are well known in which water is preheated in a tank or vessel into which a predetermined quantity of cold water has been stored. When the water reaches the desired brewing temperature, it is released from the vessel and allowed to percolate down through the ground coffee into a pot or other container from which the fresh brewed coffee is poured. Two different types of valves have been used for releasing the water from the first vessel after it reaches the desired temperature. One type of valve uses a bimetal material for opening the valve when it is heated. The second type is a snap-action device also using bimetal which operates an over-center leverage system, allowing the valve to remain fully closed until the desired temperature is reached, at which time the valve snaps completely open. Both types of valves have exhibited unsatisfactory operating life when immersed in hot water due to a combination of electrolysis and lime deposits which cause failure or malfunction of the valve after a relatively short period of use. Thus there has been a need for a valve which exhibits a much longer operating life but which is inexpensive to manufacture and install.